High spin-Chern-number insulator in α-antimonene with a hidden topological phase

• Published in: 2d materials 2024-04, Vol.11 (2), p.25033
• Main Authors: Wang, Baokai, Zhou, Xiaoting, Hung, Yi-Chun, Lin, Yen-Chuan, Lin, Hsin, Bansil, Arun
• Format: Article
• Language: English
• Subjects: As, Sb, Bi; quantum spin Hall insulator; topological insulator
• ISSN: 2053-1583; 2053-1583
• DOI: 10.1088/2053-1583/ad3136

For a time-reversal symmetric system, the quantum spin Hall phase is assumed to be the same as the Z 2 topological insulator phase in the existing literature. The spin Chern number C s is presumed to yield the same topological classification as the Z 2 invariant. Here, by investigating the electronic structures of monolayer α -phase group V elements, we uncover the presence of a topological phase in α -Sb, which can be characterized by a spin Chern number C s = 2, even though it is Z 2 trivial. Although α -As and Sb would thus be classified as trivial insulators within the classification schemes, we demonstrate the existence of a phase transition between α -As and Sb, which is induced by band inversions at two generic k points. Without spin–orbit coupling (SOC), α -As is a trivial insulator, while α -Sb is a Dirac semimetal with four Dirac points (DPs) located away from the high-symmetry lines. Inclusion of the SOC gaps out the DPs and induces a nontrivial Berry curvature, endowing α -Sb with a high spin Chern number of C s = 2. We further show that monolayer α -Sb exhibits either a gapless band structure or a gapless spin spectrum on its edges, as expected from topological considerations.